10
D. H. JOHNSON:
SMITH et al. (1970) is objective and suited to bulk processing by computer, permitting
global analyses of sea temperature to be made available for daily operational use.
Studies of the sea temperatures measured by satellite over the Indian Ocean are in
progress at the Goddard Space Flight Center, and first results have been made available
by SZEKIELDA (1970a) (see Fig. 4, DIETRICH, 1973, this volume) and SZEKIELDA,
SALOMONSON and ALLISON (1970).
Three different experiments designed to provide vertical temperature profiles using
spectrometer measurements have been tested in NIMBUS flights. They show very great
potential. An early result obtained by WARK and HILLEARY (1969) from the Satellite
Infrared Spectrometer (SIRS) data is shown in Fig. 3. The comparison with the vertical
profile obtained from a conventional radio sonde ascent made nearby is impressive. The
accuracy and resolution of the satellite values do not yet match those of the radio sonde
but these are early days and it is expected that with further research and development it
will be possible to map the global pressure fields with an accuracy at least as high as is
now possible in more limited areas with conventional data.
II. Cloud Distributions
Two main classes of satellites are equipped to provide pictures of the visible radiation
reflected during the day from the underlying surfaces by television photography. They
are the polar-orbiting satellites as in, e.g., the ESSA and NIMBUS series, and the geostationary craft in equatorial orbit known as the Applications Technology Satellites
(ATS). The former are sun-synchronous, providing a global survey of the cloud cover
once per day from heights of order 1000 -1500 km. Each picture covers an area of
diameter 30
0
latitude. ATS satellites are located at about 36 000 km over the central
equatorial Pacific and western equatorial Atlantic. They provide pictures at a frequency
of 20 - 30 minutes covering a region of diameter 100
0
latitude.
Meteorologists the world over have become accustomed to using the ESSA and
NIMBUS pictures in their daily operational work. At a number of places in the Indian
Ocean area, including for example, Singapore, Gan Island (00
0
41' S; 73
0
09' E) and
Mauritius, there are ground stations equipped to receive the daily automatic picture
transmissions. Fig. 4 is an example of one such picture. It shows a chain of clusters of
cumulonimbus clouds lying along the Straits of Malacca. The clouds were generated in
a line squall of a type known locally as a Sumatra.
Clusters of cumulonimbus clouds of dimension 0.5 to 2
0
are a common constituent
of tropical weather systems. They represent an important scale of organization. According
to the GARP Study Group (1969) cumulonimbus clusters of scale 50 km contain up to
ten cumulonimbus cells; what is visible is the canopy of cirrus cloud to which they give
rise. Fig. 5 is an ESSA 3 picture covering the northwestern part of South America on
12 April 1967. The cumulonimbus clusters are scattered over the area without any
obvious degree of organization. Cloud distributions similar to that of Fig. 5 can be found
at times over the tropical parts of each of the continents and over sizeable islands such as
Borneo. They usually exhibit a distinct diurnal variation with maximum size in the afternoon. Isolated cumulonimbus clusters and small groups are also to be found over the
Indian Ocean, but normally there is a higher degree of organization. Fig. 6 is the ESSA 3
computerized mosaic (composite cloud picture) for the Indian Ocean sector on 23 January
D. H. JOHNSON:
SMITH et al. (1970) is objective and suited to bulk processing by computer, permitting
global analyses of sea temperature to be made available for daily operational use.
Studies of the sea temperatures measured by satellite over the Indian Ocean are in
progress at the Goddard Space Flight Center, and first results have been made available
by SZEKIELDA (1970a) (see Fig. 4, DIETRICH, 1973, this volume) and SZEKIELDA,
SALOMONSON and ALLISON (1970).
Three different experiments designed to provide vertical temperature profiles using
spectrometer measurements have been tested in NIMBUS flights. They show very great
potential. An early result obtained by WARK and HILLEARY (1969) from the Satellite
Infrared Spectrometer (SIRS) data is shown in Fig. 3. The comparison with the vertical
profile obtained from a conventional radio sonde ascent made nearby is impressive. The
accuracy and resolution of the satellite values do not yet match those of the radio sonde
but these are early days and it is expected that with further research and development it
will be possible to map the global pressure fields with an accuracy at least as high as is
now possible in more limited areas with conventional data.
II. Cloud Distributions
Two main classes of satellites are equipped to provide pictures of the visible radiation
reflected during the day from the underlying surfaces by television photography. They
are the polar-orbiting satellites as in, e.g., the ESSA and NIMBUS series, and the geostationary craft in equatorial orbit known as the Applications Technology Satellites
(ATS). The former are sun-synchronous, providing a global survey of the cloud cover
once per day from heights of order 1000 -1500 km. Each picture covers an area of
diameter 30
0
latitude. ATS satellites are located at about 36 000 km over the central
equatorial Pacific and western equatorial Atlantic. They provide pictures at a frequency
of 20 - 30 minutes covering a region of diameter 100
0
latitude.
Meteorologists the world over have become accustomed to using the ESSA and
NIMBUS pictures in their daily operational work. At a number of places in the Indian
Ocean area, including for example, Singapore, Gan Island (00
0
41' S; 73
0
09' E) and
Mauritius, there are ground stations equipped to receive the daily automatic picture
transmissions. Fig. 4 is an example of one such picture. It shows a chain of clusters of
cumulonimbus clouds lying along the Straits of Malacca. The clouds were generated in
a line squall of a type known locally as a Sumatra.
Clusters of cumulonimbus clouds of dimension 0.5 to 2
0
are a common constituent
of tropical weather systems. They represent an important scale of organization. According
to the GARP Study Group (1969) cumulonimbus clusters of scale 50 km contain up to
ten cumulonimbus cells; what is visible is the canopy of cirrus cloud to which they give
rise. Fig. 5 is an ESSA 3 picture covering the northwestern part of South America on
12 April 1967. The cumulonimbus clusters are scattered over the area without any
obvious degree of organization. Cloud distributions similar to that of Fig. 5 can be found
at times over the tropical parts of each of the continents and over sizeable islands such as
Borneo. They usually exhibit a distinct diurnal variation with maximum size in the afternoon. Isolated cumulonimbus clusters and small groups are also to be found over the
Indian Ocean, but normally there is a higher degree of organization. Fig. 6 is the ESSA 3
computerized mosaic (composite cloud picture) for the Indian Ocean sector on 23 January